The instant invention is related, generally to the field of alarm devices, and more specifically to alarms used to protect operable openings, such as windows, or doors from unauthorized entry and breakage. However, other usages are possible as will be mentioned later.
Numerous alarm interlock devices have been provided in the prior art that are adapted to cooperate with foil tape. For example, U.S. Pat. Nos. 3,636,484 to Lea; 4,227,766 to Finale; and 4,271,338 to Rakocy all are illustrative of such prior art. While these units may be suitable for the particular purpose to which they address, they would not be as suitable for the purpose of the present invention as hereafter described.
At the present state of the art openings are often protected against breakage by bonding electrically conductive strips of metal tape to their surface. The strips end at an electrical terminal. When the opening is not operable, such as at store front window, the terminal is hard wired into the alarm system. When an opening is operable, a hard wire is not adequate. For simplicity we will call an operable opening "window", and it may mean window, door, shutter etc.
If it moves around a hinge, a flexible wire connection may be put near the hinge. This arrangement will not protect against breakage of the lock for which an additional protection, such as a magnetic reed, must be introduced.
For sliding windows, or double hung windows, the interlock of the window may be achieved by one of the following two devices:
(a) A springy double contact which closes the electrical circuit when the window is brought to the desired position. Use of such devices has resulted in many false alarms, and therefor the industry has in many cases switched to the second device.
(b) A plug and a socket which have to be connected or disconnected manually. The big disadvantage of this solution is that the user may occasionally forget to disconnect and thus damage the system. Even when the plug socket combination is used correctly, the repetitive movement causes one of the connections to loosen up.
At the current state of the art windows are also protected against forced opening by using a magnetic reed switch which activates when the window is forced to a position other than its normally closed one. While there is no danger of breakage to the alarm's electrical connections, this configuration does not protect against glass or other panel material breakage.